Malignant glioneuronal
tumors (MGNT) are suggested to be a new entity of
glioma defined morphologically as any
malignant glioma showing immunohistoichemical evidence of neuronal differentiation. We encountered seven cases of MGNT with
oligodendroglioma-like component and investigated alternations of chromosome 1p and 19q in these
tumors. Seven patients ranged from 33 to 62 years of age, four females and three males. Immunohistochemical study of these
tumors was performed using neuronal markers (
synaptophysin, neurofilament,
beta-tubulin,
chromogranin A and NeuN), astrocytic marker (GFAP) and Ki-67. We undertook a molecular cytogenetic study of
tumor specimens obtained from seven patients using fluorescence in situ hybridization (FISH) with
DNA probes mapping to chromosome 1p36, 1q25, 19p13 and 19q13. Histologically, these
tumors resembled
anaplastic oligodendroglioma. Immunohistochemically,
tumor cells were immunoreactive for
synaptophysin (7/7), neurofilament (6/7),
beta-tubulin (5/7),
chromogranin A (4/7), NeuN (2/7) and GFAP (7/7). The Ki-67 labeling index ranged from 4.5% to 20.7%. FISH analysis demonstrated either 1p or 19q deletion in all seven cases (100%) and both 1p and 19q deletions in five cases (71%). The 1p deletion was detected in six of seven cases (86%) and 19q deletion was also detected in six (86%). 1p and 19q deletions were present in MGNT, especially those with oligodendroglial components. We suggest that the oligodendroglial-like feature was associated with not only 1p or 19q loss but also differentiation along neuronal cell lines as
a factor of favorable prognosis in glial
tumors. It is inappropriate to make a diagnosis of
oligodendroglioma based only on morphological resemblance to oligodendroglia.